Purpose: Informal family caregivers are increasingly recognized as critical for meeting the needs of individuals with chronic diseases associated with aging. This study examined race and gender differences in perceived informal caregiver availability for participants aged 45 and older in a large national epidemiological study. Design and Methods: Cross-sectional data were collected in structured telephone interviews from 32,999 participants from the REasons for Geographic and Racial Differences in Stroke (REGARDS) study. Participants were asked if they believed that someone was available to provide care for them in the event of a serious illness or disability and, if so, to describe that person. Results: More than 80% of the participants reported having an available caregiver. Variables associated with lower perceived caregiver availability from a multivariable logistic regression analysis included being female, White, or unmarried; living alone; being older than 85; and having worse self-rated health. Spouses were the most likely caregivers for all racial and gender groups except for African American women, who identified daughters as the most likely caregivers. African American women also showed the smallest differential in perceived caregiver availability between married and unmarried (82.8% vs 75.7%), whereas White men showed the largest differential (90.9% vs 60.4%). Implications: Most individuals believe they have an informal caregiver available to them, but certain factors increase the risk of reporting no available caregiver. Increased efforts are needed to anticipate future caregiving needs, particularly for individuals who perceive a lack of available informal caregivers and may require more formal care services. Copyright 2007 by The Gerontological Society of America.